Chemical Aspects of Fractional Crystallization of Fatty Acid Methyl Esters Produced from Waste Fats

Abstract

AbstractFractional crystallization of fatty acid methyl esters (FAME) produced from waste cooking oil or animal fats was performed in a laboratory‐scale facility. The raw esters and the “winterization” products were analyzed by determining the FAME pattern, iodine and peroxide numbers as well as oxidation stabilities and element concentrations. Fractionation experiments under air and nitrogen were conducted, but no differences concerning oxidative stability were observed. By improvement of the winterization and washing the filtration residue with methanol, the enrichment of saturated FAME in one step was raised up to a technically sufficient rate of 85%. Absorption of oxygen by FAME at different temperatures was measurable. Volatile decomposition products were registrated after heating the FAME at different temperatures. It was shown that antioxidants like butylhydroxytoluene or α‐tocopherol were enriched in the phase of unsaturated FAME. This effect obviously affected the oxidative stability of the fraction of saturated FAME during winterization, although no oxidative damage of FAME was detectable at temperatures up to 20°C.